The present invention relates to a diaphragm pump including a driving mechanism that converts the rotation of a motor into a reciprocal motion and drives the deformed portion of a diaphragm.
A related diaphragm pump is disclosed in, for example, Japanese Patent Laid-Open No. 2013-36350 (literature 1). The diaphragm pump disclosed in literature 1 is integrated with a motor, and includes a pump mechanism including a diaphragm, a driving mechanism that converts the rotation of the motor into a reciprocal motion and drives the pump mechanism, and the like.
The diaphragm includes a cup-shaped deformed portion. The opening portion of the deformed portion is closed by the pump main body. A pump chamber is formed between the deformed portion and the pump main body.
The pump mechanism includes an inlet valve and a discharge valve and employs an arrangement in which when the capacity of the pump chamber increases, a fluid is sucked into the pump chamber, and when the capacity of the pump chamber decreases, the fluid in the pump chamber is discharged.
The driving mechanism includes a reciprocal motion portion attached to the deformed portion of the diaphragm, and an input portion that rotates integrally with the rotating shaft of the motor, and employs an arrangement in which the rotation of the input portion is converted into a reciprocal motion, and the reciprocal motion portion reciprocally moves.
In the diaphragm pump of this type, detection of the flow rate of the discharged fluid is indirectly performed using the rotation speed of the motor. That is, when the rotating shaft of the motor makes one rotation, the reciprocal motion portion of the driving mechanism makes one reciprocal motion, and the fluid is discharged as much as the capacity of the pump chamber. It is therefore possible to detect the discharge flow rate based on the rotation speed of the motor. As a method of detecting the rotation speed of the motor for the diaphragm pump, the following three methods are mainly used.
As the first method, a brushless motor is used as a motor, and a rotation speed is detected using a Hall device provided on a motor control board. When this method is employed, a ready-made brushless motor can be used.
As the second method, a brushed motor is used as a motor, and the motor is equipped with a device configured to detect a rotation speed, or the rotation speed is detected from the current waveform of the motor. To employ this method, a function of detecting the rotation speed needs to be imparted to the motor. Hence, a custom-designed motor is used.
As the third method, a brushed motor is used as a motor, an impeller is provided on the motor on the opposite side of the pump so as to rotate integrally with the motor, and the rotation of the impeller is detected by a sensor. In a case in which this method is employed as well, a custom-designed motor is used.
Hence, to enable detection of the discharge flow rate in the related diaphragm pump, a brushless motor or a custom-designed brushed motor having the function of detecting the rotation speed is necessary. The brushless motor or custom-designed brushed motor is more expensive than a ready-made brushed motor. For this reason, a diaphragm pump capable of detecting the discharge flow rate using an inexpensive ready-made motor is required.